700MPa级低碳贝氏体钢微观组织及冲击韧度

Study on Microstructure and Impact Toughness of 700MPa Low Carbon Bainite Steel

在热轧试验的基础上,采用光学显微镜、扫描电子显微镜及冲击试验机,研究了不同温度下700 MPa级低碳贝氏体钢的冲击韧度,并对微观组织、断口形貌及夹杂物进行了分析。结果表明,该低碳贝氏体钢的微观组织主要为板条贝氏体、粒状贝氏体、准多边形铁素体及针状铁素体的复合组织。夹杂物较为细小,尺寸多为2～6μm。当温度较高时,断口呈韧窝状,其冲击韧度较高;当温度较低时,断口主要呈解理特征,其冲击韧度较低。实验钢的韧、脆性转变温度约为-41℃。

Based on the results of hot rolling in laboratory mill,the impact toughness,microstructure,fracture morphology and inclusions of 700 MPa low carbon bainite steel were studied by impact test,scanning electron microscopy and metallographic microscope.The results indicate that the microstructure of specimen is mainly lathe bainite,granular bainite,quasi-polygonal ferrite and acicular ferrite.The main inclusions in testing steel are 2～6 μm with different morphologies.With the decrease of temperature,the fracture morphologies change form dimple to cleavage and the impact toughness also reduces.The ductile-brittle transition temperature of the testing steel is about-41 ℃.